TWU begins invasive species fish cull

TWU’s pond is the centre of an invasive species fish cull that will hopefully return the water back to a flourishing salmon habitat. Photo by Mike Rathjen

Trinity Western University in cooperation with the Ministry of Environment and the Department of Fisheries and Oceans (DFO) is beginning a lengthy and complicated project to return the pond at the entrance of the campus back into the healthy salmon habitat it once was.

It is estimated that a little over five years ago a variety of invasive species of fish were introduced illegally to the water on the Langley campus. "Someone probably dumped them in attempts to make a good fishing spot. Today we have bass, pumpkinseed and carp. None of these fish are native to BC. Pumpkin seeds and bass come from the Southern US, and carp originate from Southeast Asia," says Christopher Hall, TWU's Ecosystem Study Area Manager.

When an invasive species is discovered, it's the law to report it to the Ministry of Environment and the Department of Fisheries and Oceans. Under government guidance, TWU is beginning an invasive species fish cull. All fish over half an inch long will be weighed, identified, measured and their maturity determined before they are destroyed. Fish scale studies may also be undertaken to help determine the age of the fish. All this will help in understanding how to properly return the pond to a healthy salmon habitat. When asked if there are any salmon in the pond that will be affected by the cull Hall says, "No. Most, if not all, have been eaten by bass."

"TWU has a special permit to remove the fish, and as part of that permit you can not sell or trade them. And you probably wouldn't want to eat them either," says Erin Stoddard, Fisheries Biologist for the Ministry of Environment. Stoddard explains that bass are very aggressive predators and are extremely hard to remove once they have taken to an environment. They are heavy competitors to other fish and have even been reported to eat unsuspecting ducks.

Over the course of the summer, Hall and a researcher have been researching the pond trying to identify what types of invasive species of fish the water contains and just how big this "bad fish" population is.

The pond, or Trinity Lake as it is called, is not a natural body of water but was man-made years ago when TWU was first built. Used historically as a water reservoir in case of a campus fire, the pond was once much deeper and colder, and salmon entering it from the connected Salmon River flourished. Today the berm or raised edging around the pond is slowly collapsing and in one area, has collapsed completely, entirely closing off the pond to the Salmon River resulting in a pond which is higher in sediment and temperature, and has less flow to it. These changes have resulted in a perfect habitat for bass and other non-native fish species. "It's a good thing the pond is disconnected at this time but a major problem will occur in the winter when the banks of the pond overflow and invasive species enter the Salmon River ultimately destroying the salmon habitat. That is why we have to do the cull now to lessen this effect." says Hall.

There are, however, some benefits to the unpleasant task. A TWU vertebrate zoology class will be assisting Hall in helping to record the fish from the nets making for a great learning opportunity and outdoor laboratory.

Senior Vice President for Administration and Resources, Dale Clark adds, "We recognize the value of maintaining a sustainable salmon habitat and are pleased to be able to partner with the Department of Fisheries and Oceans and the Ministry of Environment on this very important environmental issue. Hopefully we will see a return to proper native fish populations sooner than expected because of this project."